The "heat shock" response of Drosophila melanogaster is being used as a model system of a coordinately controlled set of genes in eukaryotes. The primary transcripts and cytoplasmic RNAs are being characterized and their relationship determined. The subcellular localization of the proteins will be sought in an effort to determine the biological function of the response. Myogenic cultures derived from dissociated gastrula-stage embryo cells are being used to characterize muscle proteins of Drosophila. RNA transcripts from these cultures will be characterized. Attempts will be made to isolate specific mRNAs for gene mapping by in situ hybridization.